This invention relates to the field of determining the level of cleanliness of semiconductor processing equipment components. More particularly the invention relates to determining the contamination level of an end effector.
Many types of semiconductor manufacturing equipment utilize robotic end-effectors to transport wafers between locations. Some processes have a high probability of cross-contaminating the wafers by means of the end-effectors. Metal deposition tools, and in particular, copper deposition tools are likely to cross-contaminate the backsides of the wafers. Because this contamination can take place at any time, it is necessary to frequently check the cleanliness condition of the wafer handling devices. Due to lost production time and realignment issues, it is preferable to measure the contaminant levels on the end-effectors without requiring any disassembly. What is needed, therefore, is a system for verifying the cleanliness of implements, such as end effectors, that does not physically contact the implement and does not require that the implement be removed from the equipment to which it is attached.
The above and other needs are met by a method for detecting contaminants on an implement. A stream of gas is directed over at least a portion of the implement, to entrain at least a portion of the contaminants on the implement, and produce a contaminant laden stream of gas. At least a portion of the contaminant laden stream of gas is sampled, and the amount of contaminants in the sampled portion of the contaminant laden stream of gas is measured. The amount of contaminants in the sampled portion of the contaminant laden stream of gas is reported.
Because a stream of gas is used to entrain the contaminants on the implement, the implement is not physically contacted by something that could potentially damage it. Further, the stream of gas can be directed over the implement without removing the implement from the equipment to which it is attached.
In various preferred embodiments, the implement is inserted into a chamber, where the presence of the implement is detected, which triggers the stream of gas. The gas is preferably air, nitrogen, argon, or an inert gas. The stream of gas may be directed over the entire implement, and the implement may be rotated within the stream of gas while the stream of gas is directed over the implement.
In alternate embodiments the step of measuring the amount of contaminants can be accomplished either by counting particles in the sampled portion of the contaminant laden stream of gas with a particle counter, or by detecting the contaminants in the sampled portion of the contaminant laden stream of gas with a residual gas analyzer.
The amount of contaminants can be reported in a variety of different ways. For example, an indicator light is illuminated when the amount of contaminants in the sampled portion of the contaminant laden stream of gas is below a predetermined limit. Alternately, an indicator light is illuminated when the amount of contamination in the sampled portion of the contaminant laden stream of gas is above the predetermined limit, or two indicator lights can be provided, each with separate limits. Further, violation of the predetermined limit can trigger an audible alarm.
In a most preferred embodiment, when the amount of contaminants in the sampled portion of the contaminant laden stream of gas is above a predetermined limit, then continued use of the implement is prohibited without operator intervention. Conversely, when the amount of contaminants in the sampled portion of the contaminant laden stream of gas is below a predetermined limit, then continued use of the implement is permitted without operator intervention.
An apparatus according to the present invention has a gas discharge for directing a stream of gas over at least a portion of the implement, to entrain at least a portion of the contaminants on the implement, and thereby produce a contaminant laden stream of gas. A gas sampler samples at least a portion of the contaminant laden stream of gas, and a contaminant detector measures the amount of contaminants in the sampled portion of the contaminant laden stream of gas. An indicator reports the amount of contaminants in the sampled portion of the contaminant laden stream of gas.